The present disclosure relates to novel modulators and/or agonists of the insulin-insulin receptor signaling complex, to methods of screening for such modulators and/or agonists and to the use of such modulators and/or agonists in the treatment or prevention of disease states and conditions characterized by abnormal production and/or utilization of insulin.
The peptide hormone insulin is a major regulator of glucose homeostasis and cell growth. The first step in insulin action is the binding of the hormone to the insulin receptor (INSR), an integral membrane glycoprotein, also designated as CD220 or HHF5. The INSR belongs to the tyrosine kinase growth factor receptor superfamily and is composed of two extracellular a subunits that bind insulin, and two transmembrane β subunits with intrinsic tyrosine kinase activity. The amino acid sequence of the INSR is described in U.S. Pat. No. 4,761,371 and as NCBI Reference Sequence NP_000199.2. The INSR is expressed in two isoforms, INSR-A and INSR-B. The three-dimensional structure of the intact homodimeric ectodomain fragment of human INSR has been elucidated using X-ray crystallography (WO07/147213). INSR isoforms also form heterodimers, INSR-A/INSR-B, and hybrid INSR/IGF-1R receptors, whose role in physiology and disease is not yet fully understood (Belfiore et al, Endocrine Rev., 30(6):586-623, 2009).
When insulin binds to the INSR, the receptor is activated by tyrosine autophosphorylation and the INSR tyrosine kinase phosphorylates various effector molecules, including the insulin receptor substrate-1 (IRS-1), leading to hormone action (Ullrich et al, Nature 313: 756-761, 1985; Goldfine et al, Endocrine Reviews 8: 235-255, 1987; White and Kahn, Journal Biol. Chem. 269: 1-4, 1994). IRS-1 binding and phosphorylation eventually leads to an increase in the high affinity glucose transporter (Glut4) molecules on the outer membrane of insulin-responsive tissues, including muscle cells and adipose tissue, and therefore to an increase in the uptake of glucose from blood into these tissues. Glut4 is transported from cellular vesicles to the cell surface, where it then can mediate the transport of glucose into the cell. A decrease in INSR signaling, leads to a reduction in the uptake of glucose by cells, hyperglycemia (an increase in circulating glucose), and all the sequelae which result.
Reduction in glucose uptake can result in insulin resistance, which describes a condition in which physiological amounts of insulin are inadequate to produce a normal insulin response from cells or tissues. Severe insulin resistance is associated with diabetes, while less severe insulin resistance is also associated with a number of disease states and conditions present in approximately 30-40% of non-diabetic individuals (reviewed in Woods et al, End, Metab & Immune Disorders—Drug Targets 9: 187-198, 2009).
Current treatments for diabetes and insulin resistance are directed toward improving insulin secretion, reducing glucose production, and enhancing insulin action.
Currently, there are various pharmacological approaches for the treatment of Type 2 diabetes (Scheen et al, Diabetes Care, 22(9):1568-1577, 1999; Zangeneh et al, Mayo Clin. Proc. 78: 471-479, 2003; Mohler et al, Med Res Rev 29(1): 125-195, 2009). They act via different modes of action: 1) sulfonylureas (e.g., glimepiride, glisentide, sulfonylurea, AY31637) essentially stimulate insulin secretion; 2) biguanides (e.g., metformin) act by promoting glucose utilization, reducing hepatic glucose production and diminishing intestinal glucose output; 3) alpha-glucosidase inhibitors (e.g., acarbose, miglitol) slow down carbohydrate digestion and consequently absorption from the gut and reduce postprandial hyperglycemia; 4) thiazol-idinediones (e.g., troglitazone, pioglitazone, rosiglitazone, glipizide, balaglitazone, rivoglitazone, netoglitazone, troglitazone, englitazone, AD 5075, T 174, YM 268, R 102380, NC 2100, NIP 223, NIP 221, MK 0767, ciglitazone, adaglitazone, CLX 0921, darglitazone, CP 92768, BM 152054) enhance insulin action, thus promoting glucose utilization in peripheral tissues; 5) glucagon-like-peptides and agonists (e.g. exendin) or stabilizers thereof (e.g. DPP4 inhibitors, such as sitagliptin) potentiate glucose-stimulated insulin secretion; and 6) insulin or analogues thereof (e.g. LANTUS®) stimulate tissue glucose utilization and inhibits hepatic glucose output. The above mentioned pharmacological approaches may be utilized individually or in combination therapy. However, each approach has its limitations and adverse effects. Over time, a large percentage of Type 2 diabetic subjects lose their response to these agents. 63% of Type 2 diabetes patients fail to reach global HbA1c levels of <7% as advised by the American Diabetes Association, and are thus at high risk of developing complications. Moreover, almost invariably patients progress through the stages of declining pancreatic function. Insulin treatment is typically instituted after diet, exercise, and oral medications have failed to adequately control blood glucose. The drawbacks of insulin treatment are the need for drug injection, the potential for hypoglycemia, and weight gain. Consequently there is still an urgent need for novel anti-diabetic agents.
Antibodies binding to human INSR have been reported in Soos et al, Biochem. J. 235: 199-208, 1986; Taylor et al, Biochem. J. 242: 123-129, 1987; Prigent et al, J. Biol. Chem. 265(17):9970-9977, 1990; Brindle et al, Biochem. J. 268: 615-620, 1990; Steele-Perkins and Roth, J. Biol. Chem. 265(16): 9458-9463, 1990; McKern et al, Nature 443(14): 218-221; Boado et al, Biotech and BioEng. 96(2): 381-391; WO04/050016; Roth et al, Proc. Natl. Acad. Sci. USA 79: 7312-7316, 1982; Morgan et al, Proc. Natl. Acad. Sci. USA 83: 328-332, 1986; Lebrun et al, J. Bl. Chem. 268(15): 11272-11277, 1993; Forsayeth et al, Proc. Natl. Acad. Sci. USA 84: 3448-3451, 1987; Forsayeth et al, J. Biol. Chem. 262(9): 4134-4140, Goodman et al, J. Receptor Res. 14(6-8), 381-398, 1994; Ganderton et al, Biochem J. 288: 195-205, 1992; Spasov et al, Bull. of Exp. Biol. and Med. 144(1): 46-48, 2007; EP 2 036 574 A1.